Electrical insulator



Patented June 23, 1953 2,643,192 ELECTRICAL INSULATOR Gerard Heinrich Jonker and Pieter Benedictus Arie Schilperoord,' Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application June 11, 1949, Serial No. 98,546 In the Netherlands June 25, 1948 2 Claims. (01. 106-39) Improvements in or relating to electrical insulators This invention relates to electrical insulators.

Ceramic products obtained by reaction of barium oxide with titanum dioxide are known. According to the molecular ratio of the said oxides in the initial mixture, it is possible to produce various barium titanates and mixtures thereof with titanum dioxide which exhibit divergent dielectric properties.

Of the compounds that may come into existence in the system BaO-Tiz, barium metatitanate, BaO.TiO2, is particularly known on account of its extremely high dielectric constant (e greater than 1000). However, the tangent of the loss angle, tan a, and the temperature coefficient of dielectric constant of barium metatitanate are too high for many uses.

Furthermore, it is known that barium tetratitanate, BaOATiOz, may be produced. Barium tetratitanate has a much lower dielectric constant than barium metatitanate (e about 40) but has a lower tan 6 and a temperature coeflicient of dielectric constant of about +100.10- per C.

It has now been found that in the system- BaO-Ti0z a third compound barium trititanate, BaOBTiOz, may be formed, of which the dielectric constant and the tan 6 approximately correspond with those of barium tetratitanate but of which the temperature coeflicient is about -100.10- per C. I

An inconvenience in manufacturing ceramic insulators from mixtures consisting of BaO and T102 is that during sintering such mixtures do not readily react into a stable final state.

It has been found that the ternary system ZnO-BaO-TiOz includes compositions which permit of obtaining valuable dielectrics by sintering or melting and which with regard to their working up differ from mixtures of Ba() and TiO2 in that the desired stable final state is readily reached even at a comparatively low temperature and that a better sintering is obtained.

The invention will now be described with reference to the accompanying drawing in which:

Fig. 1 shows a ternary diagram defining regions in which preferred compositions of the invention will be found;

Fig. 2 shows a ternary diagram similar to Fig. 1 defining the entire region in whichv the compositions of the invention are found;

According to the invention, the said advantages are obtained in the first place with compositions forming products built up from mixed crystals located in the regions indicated in the accompanying ternary diagram (Fig. 1) by A and B, and also from mixtures of the said mixed crystals. The limits of the said mixed-crystal regions are dependent to a small extent on the temperature treatment chosen in the preparation. These mixed crystals may be regarded as barium tetratitanate and barium trititanate respectively in which a portion of the Ti -ions is substituted by a substantially equivalent amount of Zn -ions.

Furthermore the said advantages are obtained with compositions forming products consisting of mixtures of zinc orthotitanate with these mixed crystals. In the phase diagram (Fig. 1) of the system BaO-ZnO--TiO2 included within lines I and II connecting the mixed-crystal regions A and B to the point corresponding to the composition of zinc orthotitanate are the compositions referred to previously. The region of compositions according to the invention does not include those which are built up from only two components.

The products obtained by sintering or melting and built up from mixed crystals located in the regions A and B, as well as those from the mixtures of the said mixed crystals have a tan a lower than about 5.10- and a dielectric constant comprised between about 30 and 40, the temperature coefllcient of dielectric constant frequently having decreased to values comprised between -{-50.10* and -50.10" per C.

By addition of zinc orthotitanate, which has a dielectric constant of about 20 and a temperature coefficient of dielectric constant of about +150.10- per 0., the values of these proporties may be modified. It is evident that this is attended with an increase of tan 6 to the value thereof for zinc orthotitanate, viz. about 2010-. With a product containing a high percentage of zinc orthotitanate and having the composition 6.5 BaO48.5 ZnO-45 TiOz (point 14in the diagram) the tan 6 has, however, only decreased to about 8.10

In order to illustrate the invention, the table following hereinafter shows a number of products of different compositions the dielectric properties and the sintering temperatures used with these 3 compositions. The table also includes data for barium tetratitanate, barium trititanate and zinc orthotitanate.

4 At the most approximately half of the ZnO may furthermore be substituted by MgO. If a larger portion is substituted, a considerable incomposition in mol Sintering percent dielectric properties temper- No. a ture, v final product B50 ZnO Ti02 e :5 tg6-l0 1,320 0 so 521 10 I --BaO.4TiO2. 1,520 20 5 75 o.5 mixed crystalA. 1,320 18.5 12.5 59 ..1.5, \mixeici'ysdA-l-Tlm. 1, s20 0 75 3. 5 1350.31102. 1,300 25 5 70 1.4 mixed crystal B. 1,250 23.5 11.5 "65 1 413' D0. j g 1.320 22.5 2.5- 75 1.5 :mixed erySm1A+B.- 1,320 20 10.. 170., 5.6,. Don '1 1- 1,250 21 11 05 1.5 D0. 1 a 1,250 18 20 62 1.5- mixed 0ry'stalA+B'+ZIl2TiO4. 1,250 18 22 ,50 1.7.. Do. v 1,250 13 32 -55 2. 2 D0. 1,250 10 5.1;, :f 1,250 015 48.5 15 8 1,320 4 40 ---21 Do 1, 400 0 05.7 33.3 10 "znrrioi.

The tan 5 increases very rapidly directly outcrease" in tan oresults, as is illustrated in the side the region bounded by the lines I and II of following table: the diagram (Fig. l) and the mixed-crystal 25 regions A d B. This Seems to connected With eomposition'in mol. percent dielectric properties the production of free titanum dioxide or barium metatitanate in the final product. However, an 1 6 4 excess of some mol. percent of T102 or BaO 1n B30 Zno e dt 10 mm the initial mixture need not necessarily have un- 30 duly detrimentous consequences. With an in- 20 20 0 50 31 +25 1.1 crease of the content of TiO2 by less than about 3 2 mol. per cent or of BaO by less than about 4 20 5 15 00 28.5 +200 141 mol per cent in the initial mixture, tan 6 still re- 00 +320 195 mains below 25.10 The region-of compositions 35 v entering into consideration according to the in- Furthermore, ZnO' may be substituted by 380 vention extends, therefore, to the lines III and IV in Such manner that the te Of B is of the diagram and includes products containing ou 5 m l at t e st- It is to b n ed a small amount of free IiO2 or BaO.TiO2, as illusthat if ZnO is substituted completely by BeO, trated in the following table: a great excess of T102 is permissible without a composition in mol. dielectr. 1 sintermg percent properties i g-1 1 final product BaO ZnO T101 6 'tg6.l0

1, 300 17 15 5s 30 I 25 mixed crystal-F'IiOa. 1, 300 27 3 70 43. 5 18 mixed crystal+Ba.li0;. 1,280 27 S 45 24 mixed crystal-FBaTiOz. 1,250 25 15 60 '36 24 mixed crystal+Ba.TiOs.

In the region of compositions according to the invention the constituents may be partly substituted isomorphously by other oxides without appreciable influence on the dielectric properties, if this substitution takes place in such manner that the product obtained remains built up subhigh tan 5' resulting. The dielectric constant is then greater, but the temperature coeflicient, which is negative, is also greater, Examples of BeO substitution are illustrated in the following table:

stalzltialuy from. aining mixed crystals Of 60 Composition in mol. percent dielectric properties barlum tetra t1tanate and/or barium trititanate 7 or mixtures of zinc orthotitanate with these 1 at a 4 mixed crystals. V. BaO ZnO BeO 7'110: e 40 tgMO ZnO may be substituted by CdO in suchmanner that the content thereof is 5 mol. at 6F 30. 4 4 72 24 0 0 5 75 4. the most, as is illustrated in the follow ng table. 22 8 I 33 3.0 18 20 02 30 1.0 10 20 70 42 115 1 10 10 so 59 3.5 4 1e ec rlc Y Composltlon 1n mol. percent properties 70 Substitution of the E20 by oxides such as CaO', B50 ZnO CdO T10 5 tg 1 "SrO, PbO and LazOa, which may produce meta- 5 titanates but which cannot produce trititanates 20 10 5 55 34 5 and tetratitanates, is possible to a limited ex- 24 2 34 14 tent. The type of the mixed crystals and mixquantities were to be substituted. Notably, free metatitanate would be produced so that tan 6 would attain unduly high values. With substitution of a quarter at the most of the BaO by one 6 and mixtures are obtained to such extent that unduly large amounts of free TlO2 or metatitanate are not contained in the final product and as a consequence thereof the value tan 6 or more of the said oxides, the tan dstill remains 5 is below 25.10-*. The heating process is prefbelow 25.10- as is illustrated in the following erably continued until a stable final state is table: obtained at the temperature used. Dependent composition in mol. percent dielectric properties IBaO SrO CaO PbO peLaiot Z110 no, t Egg-109 tg 6.10

21 3 6 70 a4 0.5 18 6 6 70 as 6.8 1-1 5 19 62 38.5 -aoo 2.1 s 2 75 37 -390 4.4 14 5 19 62 3a --195 2.0 18 10 68 3o s 19 s 71 31 4.9

Finally, it is possible that about a quarter at on the composition, the initial mixtures will the most of the T102 is substituted by compounds sinter upon heating at temperatures comprised such as ZrOz, S1102 and S102. Examples of ZlOz, between about 1250 and 1350 C. and melt at SnOz and S102 substitution are illustrated in temperatures below 1450 C. the following table: It is, in addition, possible to utilise in known manner mineralisers such as CaFz, sintering di 1 t agents such as bentonite or steatite, and binders compositioninmolp e Q5 3521 such as nitrocellulose.

It is of importance that, possibly due to the B80 Zno S110, S102 e tg 5104 strong tendency to formation of crystals of the compositions according to the invention, 22 8 55 15 25 7,0 impurities may readily be absorbed by the crys- 22 s so 10 g 6 tal lattice and do not, in general, tend to give 22 8 55 rise to the formation of a separate phase in the n roduct. Conse uentl the urit 0 he It is to be understood that one of the constifi fi materials f Satisfy g i tutive oxides may be substituted isomorphously stringent requirements. For example, with by mummy oxldes slmqltaneously- An positions from which products having a tan 6 g lit g g g n '8 5 12 8 2? 90 3: smaller than 10.10 are produced, such as 25 g e 1 BaO5 ZnO-- '70 TiOz, the tan 6 is increased singeigd product thus obtained has e232 and tan 40 only to roximately 2210- d e to the presence of oxides such as MnOz, CrzO, N10 to an Fig. 2 shows a ternary diagram similar to Fig. amount of approximately 3% by vieight I 1 illustrating schematically the principal con- The insulating substance thus obtained may stituents' of the compositions according to the be used, ft having been pulverised fo the invintiontagid 115 partially replacing oxldes for manufacture of so-called drawn condensers eac cons 1 mm which, as is known er se, ma be obtained in The invention which is based on the foregoing that a plurality of oaxial cori ductors between relates to an electrical insulator consisting of a which insulating material is provided is mass, obPained by SinFering F Substan" jected to a treatment for the purpose of decreas- 1 2:323702 i;23H? gfga iggggfi g a g? g fig; ing the diameter, such as a swageing or drawing rea ment. trititanate or mixtures of zinc orthotitanate with What We claim is: A a ernary composi ion de ned w 01 y wi hin t e tuted isomorphously byother oxides to such ex- 5a region of the phase diagram of the ternary tent that the mass still substantially consists tem Shown in Fig 2 of the accompany 0f mlxed crystals ig if f fl l i i g; ing drawing bounded by angular points having and has a tan 5 3 er a r P the composition isx s2z, l6X-19Y-65Z, smallelflthan 10-10 m (aw-332, l8X27Y-55Z, 2'7X-12Y-61Z and T Insulators apcordmg to the i? Ion are 27X73Z calculated in mol. per cent, where Xinig gjg g gg gzfig gg for use m e manu' eludes BaO and one of the oxides selected from c The invention further relates to a method of igi f g g gfig fifi gi iig g g ggg preparing an insulating substance on the basis of the B210 Y includes Zno and g more than of the above-described mixed crystals or mixtures by mixing of the initial substances, for example in a ball mill, and subsequent heating.

Besides the constitutive oxides themselves also compounds of these oxides, such as titanates, and compounds which change to the oxides concerned on application of heat may be used as initial materials.

The heating process is performed in a neutral or oxidising atmosphere in such manner that the conversions into the desired mixed crystals 5 mol. per cent of CdO, not more than 35 mol. per cent of BeO and not more than 50 mol. per cent MgO, and Z includes T102 and one of the oxides selected from the group consisting of mm, $1102 and S102 in an amount not exceeding one quarter of the T102.

2. A ceramic dielectric consisting essentially of a ternary composition defined wholly within the region of the phase diagram of the ternary system X-Y-Z shown in Fig. 2 of the accom- 7 panying diagram bounded by angular points having the composition 18X -82Z, 15X19Y-65Z, 6'7Y-33Z, 18X--27Y55Z, 27X-12Y-61Z and 2725-432 calculated in mol. per cent, where X -consists of 1320, Y consists of ZnO, and Z consists of T102.

.GERARD HEINRICH J ONKER.

PIETER BENEDICTUS ARIE SCHILPEROORD.

References Cited in the file of this patent UNITED STATES PATENTS Name I Date Block Feb. 23, 1937 Number Number Number Great Britain 1946 

1. A CERAMIC DIELECTRIC CONSISTING ESSENTIALLY OF A TERNARY COMPOSITION DEFINED WHOLLY WITHIN THE REGION OF THE PHASE DIAGRAM OF THE TERNARY SYSTEM X-Y-Z SHOWN IN FIG. 2 OF THE ACCOMPANYING DRAWING BOUNDED BY ANGULAR POINTS HAVING THE COMPOSITION 18X-82Z, 16X-19Y-65Z. 67Y-33Z, 18X-27Y-55Z, 27X-12Y-61Z AND 27X-73Z CALCULATED IN MOL.PER CENT, WHERE X INCLUDE BAO AND ONE OF THE OXIDES SELECTED FROM THE GROUP CONSISTING OF CAO, SRO, AND PBO AND LA2O3 IN AN AMOUNT NOT EXCEEDING ONE QUARTER OF THE BAO, Y INCLUDES ZNO AND NOT MORE THAN 5 MOL.PER CENT OF CDO, AND NOT MORE THAN 35 MOL.PER CENT OF BEO AND NOT MORE THAN 50 MOL.PER CENT MGO, AND Z INCLUDES TIO2 AND ONE OF THE OXIDES SELECTED FROM THE GROUP CONSISTING OF ZRO2, SNO2 AND SIO2 IN AN AMOUNT NOT EXCEEDING ONE QUARTER OF THE TIO2. 